The present invention relates to a thin film magnetic head used for reading/reproducing in a magnetic disk apparatus, etc. and to a fabrication process thereof. More particularly, it relates to a method for fabricating a write head.
The need for saving images and music to a hard disk drive has quickly received widespread attention as seen in such products as video recorders with add-on hard disk drives and televisions with built-in hard disk drives. As a consequence of the increase in image data, achieving higher density has been required of the areal recording density of a magnetic disk drive. Recently, in magnetic heads, in order to achieve a high areal density exceeding 100 Gbit/inch2 there has been rapid progress in a technology shift from a longitudinal recording to a perpendicular recording. This is because thermal fluctuation of the magnetization of the medium appears when the current longitudinal recording method is used and the bit length is made smaller, resulting in it being impossible to increase the areal recording density. On the other hand, the problem of thermal fluctuation can be avoided in a perpendicular magnetic recording method because it is magnetized in the perpendicular direction. Moreover, the recording ability is improved by using a single pole head for recording because the magnetic loss is small and it has a soft underlayer on the medium side. This also becomes a motivation to shift to the above-mentioned perpendicular magnetic recording.
In order to increase the areal recording density, it is necessary to improve the track density and the linear recording density in a perpendicular magnetic head. In order to improve the track density, narrowing the track width for writing on a medium is required, concretely; there are methods such as (1) narrowing the track width of the main pole and (2) preventing side writing, etc. The following are additional descriptions of (2). FIG. 1 shows the relationship between overwrite and the effective track widths on the medium. Since at least 30 dB is required for overwrite, it is understood that the effective track width is greater than the geometric track width as shown in the figure. The reason is thought to be the side writing from the main pole, although it also depends on the medium and the flying distance between the medium and the head.
Moreover, in order to improve the linear recording density it is necessary to improve the recording gradient of the recording head. A trailing shield is proposed, in which the shield is placed on the main pole through a magnetic gap, as a method to improve the recording gradient. Using this method, the recording gradient is improved, but it is impossible to prevent side writing in the cross-track direction. Therefore, a structure was proposed in which a shield is placed surrounding the main pole with a magnetic gap. Placing this shield is expected to be effective for side writing and improvement of the recording gradient, although there is concern about the magnetic field strength, because it simultaneously shields both the track width direction and the trailing direction.
A perpendicular magnetic head is proposed in US2002/0176214 A1, in which a read head is placed at the trailing side and a wrap around shield at the leading side. Abstract No. 56 of The Magnetic Recording Conference (TMRC) 2003 discloses a perpendicular magnetic head in which a wrap around shield is provided and the return poles are placed at the trailing side and the leading side of the main pole.